


you set my soul alight

by maybesandsomedays, ohfiitz



Category: Agents of S.H.I.E.L.D. (TV)
Genre: A Whole New World: More Than 5K Exchange, F/M, hero/villain in love au, superhero Jemma Simmons, supervillain Leopold Fitz
Language: English
Status: Completed
Published: 2015-09-27
Updated: 2015-09-27
Packaged: 2018-04-23 16:17:44
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 7,573
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/4883482
Author URL: https://archiveofourown.org/users/maybesandsomedays/pseuds/maybesandsomedays, https://archiveofourown.org/users/ohfiitz/pseuds/ohfiitz
Summary: <blockquote class="userstuff">
              <p>After meeting at a party, Jemma Simmons and Leopold Fitz start dating on one condition: no one asks the other about their work. But when Jemma's secret career as a superhero finally takes off, she bumps into a revelation that forces her to make an important choice.</p>
            </blockquote>





	you set my soul alight

**Author's Note:**

  * For [mskamalakhan (blxegansey)](https://archiveofourown.org/users/blxegansey/gifts).



“So, Princess. Ready to be a superhero?”

“Yes, but certainly not in _these_.” Jemma scrunches up her nose in disgust as she holds up a pair of tiny scraps of cloth that look like a poor attempt at a…body armor? Which makes absolutely no sense, considering that the outfit barely even covers anything.

“Oh no, sweetheart, those aren’t for you.” Hunter snatches back the clothing and tosses them to a table before leaning on it and taking a swig from his beer bottle. “I never saw you as the bikini-wearing type. Are you?”

Jemma rolls her eyes. Honestly, she still finds it hard to believe that someone as blunt and stereotypically British as Lance Hunter would find a career in designing superhero costumes.

“I don’t even know why you’re still considering these skimpy designs, Hunter. In this century?”

“Hey, it worked for Tigra!”

“Did it, now? Last I heard a drone almost got stuck on her cleavage."

“ _Fine_. No bikini suits then. So now we just have to get you a nice cape and—what?”

“Nope. Haven’t you seen _The Incredibles_? No capes. And remember when you tried putting one on Matt? Skye said he looked more like a vampire than a superhero.”

Hunter takes another sip of his beer and hugs his chest, looking almost as deflated as that time the Director vetoed his plan of making all the superheroes wear hipster shades.

“Look, Hunter. It shouldn’t be this difficult. If you just let me wear something simple and functional, like the Black Widow’s—”

“We’ve been through this, Jem. Romanoff is a spy, you’re a bloody scientist—”

“And we’re both _superheroes_.”

“You’re completely missing the point here! We need something that can help you… do your thing. Maybe a lab coat? Goggles? Oh, goggles! That’s quite brilliant. I wonder if the Director would let me use that after the Great Sunglasses Ban of 2014.”

Jemma sighs and shakes her head, slowly retreating to a corner while Hunter rambles about his “bloody genius” ideas. If she knew being a superhero entailed this much planning and image management, she’d probably have never left her simple life. But she’s here now, and she just received her last trial assignment with the promise of levelling up to full-fledged superhero status—her own costume, her own superhero name, and most importantly, her own _lab_ —if she manages to take this one last minor villain down. And she’s determined to make the mission a staggering success. After all, it’s just Ian Quinn she’s up against. She can take an egoistic billionaire easily enough. All she needs to do is brush up on her undercover (read: lying) skills and stay away from any form of distraction or potential eyewitnesses, and surely, nothing can go wrong.

* * *

Leopold Fitz has prayed for very few things in his lifetime. Most of which involved monkeys. But never had he wished for what some people might call the “perfect girl.” He was completely content with his very simple, very single lifestyle, thank you very much. Building things in his secret lab, changing the world one genius invention at a time, celebrating his breakthroughs with pizza and cheap wine and Phineas and Ferb reruns—what more could he ask for? Not some ethereal goddess who’s probably too brilliant and too gorgeous for him, that’s for sure.

Frankly, his aloneness seems to be quite fitting for the life he chose to live. It was a small and quiet life, yes, but it’s still a pretty damn good one, and wishing for that _someone_ to share it with seemed like pushing it.

So when he finds Jemma Simmons one September night, with her honey-colored eyes and bright smile and a seemingly boundless enthusiasm for... well, _everything_ , he wonders what kind of miracle he did in his previous existence to deserve as much.

He’s still trying to figure that out as she introduces herself and he waits too long to respond and realizes she’s waiting, and he stammers out that his name is Leopold.

“Fitz!” he quickly corrects, almost as a yelp. “Fitz. Don’t—no one calls me Leopold.” He cringes.

She barks out a rather loud (but oddly adoring) laugh at that, and if he weren’t as nervous and embarrassed as he is, he’d probably have noticed how his heart leapt and pounded in his chest at an alarming pace, and he’d probably have realized that it was warning him that this woman was about to change his (very simple, very single, but pretty damn good) life.

They start walking together, and Fitz asks why she’s at Ian Quinn’s party.

She shakes her head. “I’d rather not talk about work.”

_Ah, yes, the perfect girl indeed._

“Oh. Okay, uh, me either?”

“Ever,” she clarifies.

“Alright,” he agrees readily. He knows already that he’d have a ten-hour conversation with her about paint drying on walls if that was what made her happy. Not talking about work was nothing. Besides, her outright avoidance of the topic reminded him of why he is at the party.

Fitz steals another appreciative glance at his new acquaintance and snaps himself back from his trance. _Focus_. He needs to focus. He is here on a mission that could potentially iron out the kinks in some of his own inventions, and while he’s still pretty sure that meeting Jemma Simmons is a miracle he doesn’t deserve, he simply can’t afford to waste this one chance at getting a peek at Quinn’s top-secret designs. Even miracles can wait, right?

Right.

But it’s just so hard to focus when Jemma is _this_ pretty. Fortunately for his fragile self-control, all of a sudden Quinn steps onto the stage and calls everyone’s attention, and both he and Jemma turn to the podium with equal levels of interest.

“Welcome, and thank you for coming! I hope you’re all enjoying the night, but at this point I would like to show all of you something that’s even better than the prosciutto-wrapped scallops. Or, well, close enough. Hopefully.”

The rooms erupts in laughter and Fitz turns to Jemma in confusion.

Jemma has been doing quite well with the undercover thing, really. Bobbi would have been proud with how _perfectly_ she nailed all that “invisible, but not weird enough to draw suspicion” attitude they’ve been practicing for months. But that was until she saw him, looking all wide-eyed and soft and out of place in a room full of rich American asswipes. She knew he was trouble, that much she’d admit, but damn if she wasn’t going to dive right into that dangerous sea. _Just a tiny bit of harmless flirtation_ , she reminds herself, and boy is she excelling in this lying business. Maybe she should transfer departments and become a spy instead. Quinn whips out a lame joke and she finds Fitz’s sky-blue eyes staring at her.

 _Americans_ , she mouths at him and rolls her eyes. His confusion makes him even cuter, she thinks absentmindedly.

“What you’re going to witness tonight is a real game changer. I mean, of course it is; I made it.” Quinn continues smugly, and Fitz begins to wonder if it was worth trading his usual Netflix marathon to listen to an endless Ian Quinn brag fest. But then he sees it, looking so complex and large and undeniably _real_ , wheeled onto the stage by several tux-clad assistants.

“New York, meet the world’s first Gravity Field Generator.”

The spotlight zeroes in on the contraption and both Fitz and Jemma let out rather loud gasps, attention so focused on the stage that they barely even notice that they’ve grasped each other’s hands.

“Appalling,” she says at the same time he whispers, “it’s beautiful” and their eyes meet for a second before the crowd starts whooping loudly and they find themselves engulfed by the sea of enthusiastic spectators.

“Do you want to step out for a bit?” Jemma asks over the loud cheering, and Fitz finds himself nodding rather desperately before he realizes how her company can put his personal mission at risk. Still, it’d probably be less suspicious if he roams around the place with someone rather than do it alone.

They make their way out of the cheering crowd and into the less-populated hallways, hands still clasped together and chests pounding, both with the thrill of sneaking into a highly secured area and the fear of something going very, very wrong.

She grins at him, and it drives a heady feeling onto his chest that almost makes him forget why he’s there in the first place. He shakes himself out of his stupor and turns his focus back to the task at hand, searching the hallway for a safe entry to Quinn's study. He glances sideways to find Jemma craning her head quite dramatically, and he realizes that they're looking for the same thing.

“So can you tell me why you’re searching for Quinn’s study too, or is that classified as talking about work?” Fitz asks, though he thinks he already knows the answer.

Jemma nearly jumps in surprise at his too-knowing question, but manages to compose herself quickly enough to put on what she hopes is a flirty expression.

“Maybe I’m looking for a place to make out with you,” she says, biting her bottom lip and sliding a hand from his shoulder down to his chest. His surprisingly firm and just very slightly toned— _No. Bad Jemma._ She flicks her eyes back to his face and tries to recall all her espionage lessons with Bobbi.

_How to Deal With Potential Eyewitnesses. Step 1: Distract, but do not get distracted._

Fitz stops short and stares at her. He definitely had not known the answer.

“Now!” she says suddenly, pushing him in the direction of the study, and Fitz’s heart sinks. He should’ve expected that she’d only been using him as a distraction—there was no way she would ever want to kiss _him_.

Once they’re safely inside the study, Jemma hurriedly locks them in. “Sorry about that,” she says, and she really is truly sorry she had to do what she did. “I saw the opportunity, so the snogging will have to come later.”

“Yes!” Fitz nearly shouts, then clears his throat in an attempt to regain his composure. So much for trying to be smooth. “I mean... yeah, sure. Later. If you want.”

She flicks her eyes up and down his body and licks her lips. “Oh, I do.” She chuckles, and wishes it came out sultry and not as ridiculous as it sounded in her head. She usually has more self-control than this. What the hell is happening _now_?

“Okay. So here’s the deal. We obviously both need something from this room, and we need each other to not get caught. How about we take turns keeping watch while the other does whatever they need to do?”

Fitz nods. “Sounds good. You can go first,” he offers, and takes his place by the door, fixing his prototype stick-on camera to the other side of it to monitor the hallway.

Within a couple of minutes, there’s a light tap on his shoulder and Jemma pushes him out of the way and takes his spot, and Fitz quickly searches the room himself.

As he rummages through the massive mahogany cabinets, Fitz starts to doubt his impulsive decision to team up with a stranger for something that can finally answer the questions he’s been stuck on for _months_. What if she’s planning to destroy Quinn’s work? What if she’s a cop, or a spy, and she’s here to wipe out Quinn’s designs?

Fitz shakes his head lightly. _No. It can’t be. She doesn’t look like the kind of person who would be interested in sabotaging the Gravity Field Generator. But then again,_ betrays the voice in his head, _she didn’t look like the kind of person who would flirt with an awkward boy and then propose to snoop around a highly secured mansion together. And yet here you are._

But just as he’s contemplating how it doesn’t sound so bad to do more snooping with easily the most beautiful woman he has ever met, Fitz catches sight of the edge of a sheet of diazo paper poking out of one of the drawers. He opens the drawer and rolls out the sheet, revealing the detailed blueprint of the Generator.

It only takes him a minute or so to realize just how dangerous the machine is, and pinpoint the exact part he has to disassemble to disable the Generator in its entirety. The only problem is that the machine elements are held together by very specifically shaped and sized weld nuts. Now, if he can only find the custom wrench that he’s sure is stored in Quinn’s safest room— _oh, Jemma..._

He snaps pictures of several more of Quinn's blueprints and business plans before he rejoins Jemma, who opens the door a crack and peeks out to make sure nobody’s nearby. “Go!” she whispers, and they rush out the door and Fitz closes it as quietly as he possibly can.

They fast-walk to the grand spiral staircase to rejoin the party before Quinn or anyone else notices their absence, trying not to look suspicious, and they stop to look around a corner. After they are sure that all corners are clear, they quietly sneak into the backstage, where the Generator has been stored after the initial presentation.

“Give it to me.” Fitz says in a rush, and Jemma quirks an eyebrow at him. “Listen,” he says firmly, not wanting to waste time, “I know you have the wrench, but it’s not as simple as unscrewing the bolt. Trust me. I’ve seen the blueprint and I know how this thing works.”

“And you think I don’t?” Jemma says, folding her arms across her chest in indignation.

“Not as well as I do, I don’t think so.” Fitz snaps back, smirking. “Just give it to me, Jemma.”

Jemma bites her lip thoughtfully. _He’s probably right, Jemma. Now’s not the time to be stubborn. Besides, he does look like he can do marvelous things with his bare hands, and his long, slender fingers, and…_

“Oh, screw it,” she huffs, shoving the wrench forcefully into his hand.

Working quickly with swift, nimble fingers, in one movement he’s disabled the gravitonium device forever, hopefully in a way that will be thought of as a mistake, not evidence of tampering.

In a blink, Fitz sees Ian Quinn heading their way. Panic rushes through him; Quinn can’t recognize him. He turns to Jemma.

“Can I kiss you?”

Despite looking shocked, she nods, rather enthusiastically, and he quickly closes in before Quinn reaches them.

Fitz has spent most of the night imagining what kissing Jemma would be like. But—and he knew it was completely unscientific—but he was not expecting fireworks to go off in his brain and his heart to leap and soar even farther than it had upon meeting her. He didn’t expect it to feel as easy as breathing and as warm as a cup of hot chocolate on a wintry December night, and he certainly didn’t expect it to feel real.

She gasps, and he feels the slight opening of her mouth calling him home. Fitz surrenders to her pull for a second or two but then a door closes loudly behind them and they break apart, and it is over so soon. Too soon.

All he wants to do is stand there and hold her in his arms and look at her beautiful face for the rest of eternity, but he reminds himself that they need to escape fast, and he glances around to check.

Ian Quinn is still watching them. But he walks away and Fitz breathes a sigh of relief, although he’s tempted to pull out a megaphone and yell for Quinn to come back if it means he can kiss Jemma again.

 _Thank you_ is what he means to say, but instead what comes out is, “You’re like a supernova.”

She blinks, and before she can say anything Fitz continues, “An explosion so bright that it briefly outshines another galaxy.”

“I know what a supernova—”

“And you just made a supernova in my brain. You could outshine even a supernova.”

She grins at him and tilts her head up to kiss him again, and Fitz wonders again if he’s dreaming or possibly dead and in Heaven kissing an angel.

“Good thinking, by the way,” she says when they pull apart, lips still barely a breath away from each other. “With the kiss, I mean.”

Fitz lets out an exaggerated huff, feigning offence. “And here I thought you were talking about my very impressive engineering skills. But okay, go on, never mind that I just disabled the machine that could’ve changed modern history.”

“Well, yes, that too. But I rather think you have even more impressive kissing skills, Mr. Fitz,” Jemma says breathily, skimming her thumb across his lower lip.

Fitz answers by kissing her thumb and flashing a shy smile that’s already becoming her favorite.

“Do you want to come back to my place after this?” Jemma asks just as Fitz blurts out, “Do you want to go out sometime?”

Fitz’s face turns red and he starts nodding. “Yes, I would, uh, I would love to come back to your place.”

“And I’d love to go out sometime,” Jemma adds with her lips close to his again.

Fitz sucks in a quick breath in surprise. “Okay. Yes. Yes, thank you.”

Jemma peeks at a nearby curtain. “We should really get back to the party,” she says, sighing regretfully.

Fitz tears his gaze away from her and follows hers. “Yeah. Probably,” he agrees, licking his lips and still tasting her strawberry chapstick.

As they’re nearing the end of the staircase leading to the party floor, Jemma turns to Fitz and holds out her hand. “Dance with me,” she says, and Fitz would never have thought that those words could sound seductive but oh, they do.

Fitz takes her hand, and they glide out onto the dance floor together. He pulls her close as the song switches to a ballad called _On the Wings of Love_.

“I really did want to kiss you earlier, you know,” Jemma says as they sweep across the floor, looking up at him through her eyelashes. “I’m glad you did.”

“I'm glad I did, too,” Fitz says with a cocky smirk, and she fights the urge to kiss it away.

“And do you still want to come to my place and go on a date?”

Fitz nods so fast that he looks like a bobblehead, and Jemma smiles.

“Let’s go then. Whenever you’re ready.”

“I'm ready,” he breathes and she leads him off the dance floor and outside, all the way to her flat and to her bed.

* * *

“Congratulations on passing all your test missions, Dr. Simmons. I suppose I should also congratulate you for your formal promotion as a superhero, but, you’ve always been one, Jemma. I always knew you’d make it.” Coulson flashes her one of his rare full smiles, and Jemma automatically returns his grin.

He continues, “As a ‘Welcome To Superhero Hell” gift, you will now be heading the Big Bang case. Oh, and don’t forget to file for your official superhero name before the end of the week. We have to get your records sorted before you start with this guy.”

Jemma Simmons blinks at him for a moment, unsure if she heard right. But of course she did; she’s been hanging on Director Coulson’s every word since before the meeting had even officially started.

So she stands up and said “Thank you, sir,” a bit too eagerly, and takes the file handed to her. She’s been following the series of explosions and “accidents” that have been plaguing the town even before S.H.I.E.L.D. took on the case. And now she has the chance to stop it. She has the chance to prove herself as a worthy superhero and make a name in Hell’s Kitchen. _This_. This is what she’s been waiting for since she was recruited as a seventeen-year-old with two Ph.D.s and an unending supply of science to save the world. Sure, she doesn’t have superpowers like Skye or heightened senses like Matt, but she’s certainly more than smart enough to replicate them, and it’s high time the Director recognized her (clearly) unparalleled potential.

Jemma had never thought she’d be a superhero in training, not even in her wildest dreams. She had a good plan for at least the next twenty years of her life, all laid out in neat rows and perfectly calculated outlines. She was going to complete her Ph.D.s, maybe aim for a third one, then work in one of the best medical research facilities in the world. But that was until aliens invaded New York, and suddenly a whole new realm of possibilities and threats opened up and she couldn’t resist the temptation of saving the world (maybe even the universe) with science.

Before opening the file, she sighs and irritatedly crosses out BIG BANG in the page of her notebook dedicated to ideas for her superhero name. It had been definitively circled in red pen and everything, and she was going to file to have it her official superhero name after the meeting, and now she has to start over all thanks to people calling this maniac _her_ name.

“Bad day?”

Skye’s voice nearly makes her jump, and Jemma heaves a deep sigh. “Not really.”

“Come on, Jemma. I could practically sense your rage from the basement.”

“It’s just…” Jemma starts, not knowing how to vent her predicament without sounding too shallow. “He stole my name.”

“Who? The Big Bang? Pretty sure he didn’t give himself that name, Jem.” Skye chuckles, and Jemma shoots her a threatening glare.

Skye doesn’t flinch.

“Besides. You have to give it to the man. Those weekly explosions really are kind of a big bang, you know.”

Jemma continues to glare at her, clearly unimpressed. “Well, then I’m the bigger bang,” she pouts, crossing her arms and holding her head up even higher, clearly offended by this praise for the _enemy’s_ explosions. She can make things explode, too. She’ll show them.

“That doesn't sound much like a superhero name.” The two women turn to the voice as its owner enters the room, smirking as he hoists himself up a desk and places his walking stick beside him.

“Yeah, because _Daredevil_ is so original.”

“I can feel you rolling your eyes, Skye. And how much better is _Quake_ , anyway? You sound like a brand of oatmeal.”

“Shut up, Matt Murdick.”

“Guys! Can you please just help me here? Coulson just gave me this huge assignment and I can’t muck it up. This could be my big break! My claim to greatness. And I _definitely_ can’t claim greatness with a subpar superhero name.”

“Okay then..." Skye starts, hopping up to sit on the table beside Matt. “Super Science?”

“Biochemma?”

“Lieutenant Lab?”

“Miss Molecule?”

“Atomic Angel?”

“Supernova,” Jemma says suddenly. She thought Fitz was being ridiculous, but it works. It’s perfect.

Skye considers. “I like it,” she says finally, and Matt nods in agreement, and they soon exit the room to leave Jemma to her file.

She memorizes everything in the manila folder that day at work, noting every bit of detail and searching for possible connections. By the end of the day, she’s all knackered yet still incredibly happy about her new assignment. Luckily, Jemma knows exactly what she needs to relieve her stress and celebrate at the same time.

* * *

Fitz kisses Jemma deeply and passionately when she shows up at his door with food and a bottle of wine, and she thinks that between meeting her new boyfriend and _finally_ , finally being labelled as an actual superhero, this might be the best month of her life.

He eventually (reluctantly) lets go of her, and Jemma kisses his pouting lips one last time before dragging him to the couch. She digs into the pizza and he takes his place behind her, rubbing the tense muscles of her shoulders in silence. He doesn’t ask about her work, doesn’t say a thing about how she’s evidently stressed about something, and she’s grateful for it. She likes Fitz; she really does. He’s sweet and caring and adorable, but probably her favorite part of their relationship is that he respects that one rule she set and doesn’t demand to know much. If she were being honest, she’d say she recognizes that frequent look in his eyes, the one that says he wants to ask. But she’s thankful that he doesn’t, because she also knows for a fact that even at this early point in their relationship, she’d tell him in a heartbeat.

So it’s probably better this way. To enjoy each other’s company without falling in love. She just can’t… she can’t afford that right now. Not when she’s finally been given the big break she’s always wanted. Truthfully, she’s not sure if she can afford it ever. She’s called to be a superhero, and heroes are called to sacrifice.

Fitz presses his thumb down a particularly tense knot, and Jemma sighs in relief. As soon as the pizza’s gone, she plans on getting him to untense a lot more muscles than just the ones in her back.

* * *

It wasn’t supposed to go wrong. Jemma has been on this villain’s tail for weeks, and she had prepared a thorough plan of combat with the entire S.H.I.E.L.D strategic team. That, and she’s a _superhero_ , for god’s sake. She was supposed to be strong and invincible and walk out of every fight with a confident gait and her Lab CapeTM swooshing gracefully in the wind.

She wasn’t supposed to bleed, and she wasn’t supposed to hurt, and most of all, she wasn’t supposed to _fail_ and jeopardize public safety.

And yet here she is, limping helplessly in a dark alley and a numbing sense of guilt and anger that she wasn’t strong enough to take the guy down. She passes by an unattended locker room and makes a quick and painful change of (stolen, er, _borrowed_ ) clothes before practically crawling back to the streets. Before she realizes it, she’s heading to an apartment three blocks away from her own, and she’s startled at the fact that her feet automatically brought her here—to him—when she desperately needed to feel safe.

“What the hell, Jemma?!” He—there’s only one ‘him’ for her now, maybe forever, she suspects — bellows as he opens the door, and the gentleness by which he takes her face in his hands drowns out the loudness of his voice.

“Fitz, please. I just need to rest for a bit.”

“Okay. Okay, I’m sorry.” He takes her hand and leads her to the bed, pressing a light kiss to her forehead after she lies down.

Jemma stares at the ceiling while Fitz putters around the flat to retrieve the medical kit. She sighs then sits back up, resigned to the fact that she would have to tell him _something_ about why she got hurt sooner or later.

“I’m a scientist,” she blurts out when Fitz comes back with the first-aid kit and a cup of tea. She takes a deep breath. “I’m a scientist, and it’s my duty to protect people, and that’s all I’m saying about what I do.”

“Jemma, that is most definitely not what being a scientist means.”

“Well it is for me!” she shouts, and the cut on her forehead burns sharply, but she wants, she needs him to understand how important her work is to her.

“I don’t like this.” Fitz says, pinching the bridge of his nose. “I don’t like this at all.”

“Well, you’ll just have to get used to it,” Jemma retorts, bristling.

“Jemma! What if you get killed out there doing _science_? I don’t know what I would do if you—” He stops and sighs heavily. “Please. Please don’t do this to yourself.”

“I have to, Fitz. Please try to understand that. I’ll be fine, this is just...a minor mishap.”

Silence pervades the room as Fitz paces back and forth, running his hands through his hair.

“Okay. Okay, I’m gonna stay out of it. But please, Jemma, always come to me when you’re hurt, okay?”

Jemma nods, head still aching but feeling thoroughly relieved by his concern.

“Come here,” he says, taking her into his arms and pressing gentle kisses to her face. “At the very least, don’t do anything until after you’ve healed, yeah?” She nods agreement against his chest.

“You are the best, bravest person I’ve ever met,” he says softly into her hair, kissing the top of her head. “I’m proud of you. But still be safe.”

“I promise.”

“I can’t lose you, Jemma. The world can’t lose you.”

“I’m sorry, Fitz. Thank you. For everything.”

“Always, Jem. Always.”

* * *

A few days later, Fitz wakes up unusually early and with a wide smile on his face. Today. Today is the day he finally perfects the night-night guns and grenade. He is _sure of it_. Last night was fantastic, possibly the best night of his entire adult life, and apparently having sex with Jemma is…well, _stimulating_ enough that sometime between his third and fourth climax, he suddenly remembered this one paper on the potential applications of neurotoxins that he came across with ages ago. And just with that one brief flash of memory, everything clicked together. It was the _Eureka!_ moment he has been waiting for for months, and it all happened with the most beautiful creature on earth riding his cock.

Leopold Fitz is a scientist, and all evidence points to the inevitable conclusion that he is maybe, probably, definitely in love with Jemma Simmons.

Therefore, he thinks everything might be even more amazing if he combines the two best things in the universe. As soon as the Night-Night products are completed, he’ll finally have an invention that’s clever enough for him to show Jemma and hope that she’ll be impressed.

It’s all he wants, really. To impress Jemma. And this idea for how to do that, finishing the Night-Night collection that will really show off his true genius, has been brewing in his mind ever since she gave him the vague description that she’s a scientist.

He’s not the best biochemist, that much he’ll admit. Most things in that field gross him out. But he does what he can remember to calculate the appropriate dose of dendrotoxin and fills the bullets with it, and tests the pistol out on a lab rat he’s named George.

George’s heartbeats remain steady, and a few hours later, he’s up and eating, completely fine. Fitz whoops in celebration, raising his arms to the air, and pulls out his phone to call Jemma.

“Jemma! Hi! Um, are you busy tonight?”

“Not at all! You want to have sex?”

“That too, but I was hoping you’d want to maybe go out to dinner? Me and you. Someplace nice.” He puts the grenade in his hand down on the windowsill.

“I’d love to! What’s the occasion?”

“I, uh, I had a great day today. I want to celebrate with you.”

“Oh, Fitz, congratulations! I’ll see you at six?”

“Yeah. Six,” he agrees, grinning and leaning his elbow on the windowsill.

He knocks it over and it slips out the window without him noticing.

* * *

_Explosions are currently being heard near the Empire State Building. We believe this to be another act of the mysterious and elusive supervillian known only as the Big Bang…._

Jemma goes faster and faster, the S.H.I.E.L.D. radio echoing in her head. This time. This time she’s got him.

Then she can finally prove that she’s a worthy superhero.

She rushes to the source of the explosions, following the clouds of smoke and squinting to try to keep it out of her eyes.

But when she gets there, the area is completely void of people. It’s simply a garbage dump, and a small area is now clear of trash and in its place sits the tiny shell of the weapon she hopes belongs to her archnemesis.

Donning her gloves, she carefully collects it into a biohazard evidence bag.

Jemma squints at the tiny label attached to the weapon and raises her eyebrows. _Night-Night Grenade?_ That is the most ridiculous name she’s ever heard in her life, and she’s seen Skye change every mention of S.H.I.E.L.D. on the internet to _Super Hero Initiative against Evil Loser Dudes._

Jemma’s annoyance at the stupidly named (but admittedly clever) weapon intensifies when she brings it back to her lab and identifies the substance enclosed in the bullets.

Dendrotoxin.

She frowns. Several years ago, she published a well-received paper on the possible use of neurotoxins in non-lethal weapons, and she has since regarded it as the highlight of her scientific career.

 _Great_. So apparently, her nemesis is not just into street crimes but intellectual property violations as well.

But, she considers, at least now she has a lead of some sort. She now knows that the Big Bang must be intelligent, if he could grasp her paper enough to use the technology she had described and then figure out how to make his own grenade.

The more she looks at it, the more impressed she is, and the more annoyed she is that she’s impressed by it. Whoever built this thing has to be the smartest person she’s ever come across other than herself.

She can feel her blood boiling at this person who probably thinks they’re smarter than her. Using technology she discovered? He’s baiting her, and she knows it.

And even through her fury, she can’t help but be excited that she finally has an archnemesis.

* * *

When Jemma arrives at Fitz’s door that night, he kisses her the way he always does, as though he’d lived in a dark, bleak world until the moment she arrived and she is his only light in the darkness.

“I’ve been waiting for you,” he says excitedly, pulling on her hand. “I want to show you something.”

“Is it your dick? Because I’ve seen that, and I rather like it,” Jemma teases, staring straight down at his crotch.

Fitz immediately blushes as red as a lobster. “No, not that—well, maybe later, hopefully, but uh—just—come see this, please. I’ll stop talking.”

She obliges and lets him lead her to a back room of his apartment she’s never seen before. When they step through the door, she gasps; it’s a lab very similar to her own.

“Fitz! This is incredible! You like science?”

“I’m an engineer, actually, yeah. A fucking excellent one, if I may say so myself.” He chuckles proudly. “And I have a surprise for you. Stay there.”

He returns moments later with some sort of gadget his hand and another bulky object under his arm, which he lays down on the table.

“So, uh, I read this paper a few years ago, and I really liked it but I couldn’t seem to trace it anywhere now. But anyway, I couldn’t think of how to finish my project, and then we were, um, _together_ , and I remembered this—thanks for that, by the way—and well, here.”

The things he’d brought out are a tiny grenade and a gun.

“They use dendrotoxin,” he says proudly. “Non-lethal. I call them the Night-Night Gun and the Night-Night Grenade.”

 _Night-Night Grenade_. A flash of the Big Bang’s weapon swims in her head and a queasy feeling settles in her stomach. Her head pounds and she thinks she might vomit. She realizes Fitz is looking at her in expectation, waiting for her reaction.

She wants to tell him they’re brilliant. She wants to tell him that she’s impressed that someone could use her research in that way, that the uses for these weapons are endless because they don’t kill, and that she loves them.

“That’s the stupidest name I’ve ever heard,” she whispers, wishing she could sink into the floor, be swallowed up by the ceiling, do _anything_ but be right here, in this moment.

Then she lets out a choked sob and turns and runs, tears streaming down her face.

* * *

_An Analysis of Non-Lethal Applications of Neurotoxin Exposure_

_Author: Dr. Jemma Simmons, Ph.D._

Fitz stares at the byline in horror. He finally tracked down the author of the paper in order to give them the proper credit, and it’s his _girlfriend_. Well, ex-girlfriend now, since he’s sure she’ll never want to see his face again after the Night-Night debacle.

At least now he knows why she was so upset, though. He would be too if someone had stolen his research, and it wasn’t like she had known he’d give credit where credit was due.

And if, against all odds, she’s willing to listen to him, he’s going to do everything he possibly can to try to make things right. But the moment he picks up the phone to call her, his doorbell rings and Jemma’s standing in front of him, her eyes red and puffy from crying.

Fitz’s heart stops dead in his chest. “Jemma, no, what’s wrong?”

“Sit down, I have to tell you something,” she chokes out. She takes a deep breath, and then, “Fitz, I’m a superhero.”

Fitz gives her a blank stare, and she continues. “I work for S.H.I.E.L.D. I’m a superhero named Supernova. I don’t have any powers but I create...things through science to save people and fight crime. And my nemesis—well, my first one at least—is the Big Bang.”

“Oh, I’ve heard about him!” Fitz says excitedly, then instantly frowns at the implication. “Jemma, no, why are you fighting that guy? You’ll get hurt! You already were—is that why you were so beat up that time?”

“No, you don’t… you don’t get it. It’s you, Fitz,” Jemma whispers in horror. “You’re the Big Bang.”

He’s silent for a moment, and then—“So all this time, you’ve been banging the Big Bang,” he jokes.

Jemma groans and rolls her eyes, clasping her hands together behind her neck. “Oh, _Fitz!_ ”

He winces and shakes his head, running his hands down his face to contemplate what she's saying. “Sorry. But Jemma, I’m not the Big Bang! I’m not—I swear, Jemma, I never meant to hurt anybody. Did I? Oh, god, did I hurt you?”

She shakes her head. “It’s an accident, I think. After I saw your lab—I think it’s just you testing out your designs.”

Fitz runs his fingers over his hair. “Fuck, Jemma, I’m so sorry. I didn’t know—if I’d known that I was causing you so much trouble—”

“It’s not your fault.” Noticing her crumpled face, looking like she’s fighting back all of her emotions, Fitz pulls her into a hug, and Jemma silently breaks down.

“I’m a terrible superhero and a terrible person, Fitz. Look at me, dating my supreme enemy and going after _you_.” _Look at me, falling in love and then destroying everything._

“Jemma, no, stop that. I think—I think I’ve always suspected it. Maybe. That you’re…what you are. You are the stuff superheroes are made of, Jemma. You’ve always done the right thing, always made the right decisions. Maybe except me.”

“Fitz, you are the rightest decision I’ve ever made. And I want…I want to believe you’re good,” she confesses.

“I do, too.”

“I have to turn you in.”

“I know.”

“I don’t want to. I don’t think you deserve it.”

“You have to.”

“I won’t.”

“It’s your job. Jem, you have to do this. I understand. I don’t care. I hate knowing that I was the one scaring innocent people and putting you in danger.” She doesn’t say anything, but she shakes her head against his chest. “And then you’ll be a big-name superhero, the one who caught the Big Bang.”

“It’s not worth it. I don’t want it. I want you.”

He smiles.

“I’m already yours.”

* * *

“Nope, no leads on the Big Bang, sir,” Jemma lies, trying not to look nervous and sure she’s failing. She prepared for this. She rehearsed this. She should be fine, she tells herself.

Jemma can sense that Coulson seems suspicious, and her brow furrows and she opens her mouth to continue her prepared spiel on just _why_ there have been no leads. Before she can do so, however, the door to Coulson’s office bursts open.

“Hello, sir. My name is Leopold Fitz and I’d like to turn myself in. I’m the Big Bang.”

“No!” Jemma screams before she can stop herself.

Coulson’s eyebrows shoot up and his eyes widen. “Agent Supernova, do you know him?”

She sags her shoulders, defeated. “He’s my boyfriend,” she admits. “But sir, I didn’t know!” It’s probably the worst lie of her entire life, and she thinks Coulson knows it, but he doesn’t say anything more.

Instead, he turns to Fitz. “You’re under arrest for multiple explosions and being the supervillian known as the Big Bang.” He pulls out his handcuffs, and Fitz obediently holds out his hands.

“Fitz, no, please don’t do this,” Jemma begs.

“I have to! It’s the only way people will feel safe!”

“It’s not your job to make people feel safe, Fitz! Don’t you remember? That’s not what being a scientist means.”

“It is, if I choose to. That’s what you taught me.”

Jemma moves closer, intending to hug and kiss him, but Coulson steps in between them before she can reach him, just as the guards arrive.

“That’s enough,” he says sternly, and two guards take Fitz by each arm and begin to escort him out.

“I love you, Jemma,” he yells back.

A tear rolls down her face, and he’s already gone before he can hear, “I love you too.”

* * *

Fitz wakes up with a start as the intricate locks of his cell door clink open, and Jemma’s boss—Director Coulson, he thinks—walk into the room with the kind of gait he’s only ever seen in those horrible American spy movies.

“I can’t believe I’m saying this but, we need your help, Mr. Big Bang.” the man says, and Fitz notes the exhaustion and resignation in his voice. Must be a tough life, being in charge of the people in charge of saving the world.

“Fitz. Uh, it’s Fitz, sir.”

“Right. Mr. Fitz. Well, there’s a problem and Agent Supernova tells us you’re an engineer. A very good one, at that—”

“I’m a genius, sir, actually. Rocket scientist and all that.”

“Right. But as I was saying, your, uh, _genius_ skills will be needed for this particular villain we’re having difficulty with.”

Fitz nods and follows Coulson out of the room.

* * *

“Good job, Mr. Fitz,” Coulson says wearily.

“Dr. Fitz,” Jemma corrects. “He’s a doctor.”

“Thank you, Dr. Fitz. We couldn’t have done this without you and your expertise. And your Night-Night Gun.” Coulson holds out his hand, and Fitz shakes it.

“Thank you for giving me the opportunity, sir. And uh, sorry about all the explosions. I never meant to hurt or scare anyone.”

Coulson studies him for a second, and his features soften as he begins to speak. “I believe that now. But you still caused a huge amount of damage, Fitz. We’ll take your assistance in this mission to consideration, but you’d still have to go through our standard clearing process. And I tell you, it’s not an easy one. But maybe, maybe when all of this is over, you’d consider working with us? We could use a brilliant mind like you at S.H.I.E.L.D. If you’d like that, of course.”

“Oh, I don’t know about that sir, I’m not exactly superhero material.”

Coulson hands over a business card. “Well, if you ever change your mind. We could set you up in a lab and have you work with Agent Supernova.”

“I’ll take it.”

“Right, then. I’ll give you two a moment to yourselves then we’ll get you started on that clearing process.” Coulson nods at them and throws a knowing smile in Jemma’s direction before walking out of the door.

“What the hell was that nonsense?” Jemma blurts out when Coulson has left the room.

“What? It’s true. I’m the exact opposite of superhero material, Jemma. Not when I… not after I’ve hurt all those people.”

Jemma stands up on her toes and kisses him. “You are what every superhero should be. And besides, you just chose to help more people than you ever accidentally hurt.”

“I… I don’t know, Jemma. I don’t think I deserve it. I don’t even think I deserve _you_.” He stares down at his feet.

Jemma cups his jaw and tilts his face up, urging him to look at her. “Leopold Fitz, you are the stuff superheroes are made of, and you’re all the stuff I need. Remember that.”

“Yeah?” Fitz says with a hopeful smile.

“Yeah,” Jemma answers, pressing another brief kiss to his lips. She slides her hands down from the back of his neck and rests her palms against his chest, biting her bottom lip as she looks up at him with a teasing grin.

“So, Dr. Fitz. Ready to be a superhero?”

**Author's Note:**

> This is a gift for mskamalakhan as part of the More Than 5K Exchange, who requested a Grey's Anatomy AU. Unfortunately, neither of us has ever seen Grey's Anatomy, so we're very sorry about that and we went with her general AU prompt of a hero and villain in love. Hope you liked it!


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